General terms

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Streams

• General terms
• Introductory Concepts
• Important physical attributes
• Important biological attributes
• Factors controlling stream communities
• Organic matter dynamics
• The River Continuum Concept

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General Terms

• Lotic
• Hydrology
• Potemology
• Allochtonous
• Autochtonous
• Wash load
• Bed load

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Introductory Concepts

• Unidirectional flow
• Flow from uphill to downhill
• Linear form
• Streams are more or less like
• Where lakes are more or less like

More area isolated from landscape
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• Fluctuating discharge
• Discharge amount of water flowing through a
  particular reach at any given time volume/time
• Large fluctuations within a short time, i.e.
  flash floods
• Unstable bed morphology
• Stream beds and channels constantly change
  through erosion, deposition, etc.

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Important Physical Attributes

• Stream Order- designates the stream size within a
  watershed
• The Sacramento River near Sacramento is a 7th
  order stream
• The Mississippi River in New Orleans is a 12th
  order stream
• The Amazon is a 16th order stream

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• Gradient stream slope
• Major factor in water velocity
• Velocity affects wash load
• Amount of wash load affects biological organisms
• Discharge volume of water in a stream segment
  at any given time
• Current velocity of water in the stream

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• Channel Morphology channel shape
• Catchment geology ? impact on stream biota
• Catchment area drained by any given stream
• Soils within the catchment affects the streams
  chemical properties
• Ex desert soils are low in N ? ? desert waters
  are also low in N and have a lot of N-fixing
  algae (i.e. blue-greens)

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Distinguishable Biological Attributes

• Biological action mostly on the stream bed ?
  benthic organisms dominate, especially
  macroinvertebrates
• 95 of benthic invertebrates are aquatic insects
• Most have adaptations to maintain their position
  in the stream, such as claws or body shape
• Amphibians vary in importance

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• Most plant life is periphyton
• Aufwuches attached conglomeration of benthic
  algae, bacteria, and fungi found in a stream
• Aufwuches is now referred more as biofilm
• Fish are the dominant nektonic group
• Others, like otters, can also be sometimes found

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Factors Controlling the Structure and Function of
Stream Organisms

• Current Speed
• Organisms prefer different current speeds
• Current speed also important for erosion and
  deposition
• Ex Slower currents ? more deposition ?
  deposition may clog gills of aquatic insects

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• Size and composition of stream substrate
• Diversity is correlated with the substrate
  particle size
• The highest diversity is on cobble to gravel
  sized substrates
• Sandy bottoms have the least diversity
  periphyton and other organisms cannot cling to
  sandy bottoms

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• Stream water temperature
• Organisms have different optimal temperatures
• largely due to dissolved oxygen needs
• Temperature moderates chemical reactions,
  generally,
• ? temperature ? reaction rate

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• Food and nutrient requirements
• Ex There is a lack of Ca in Alaskan watersheds
  and greater Ca solubility ? snails have brittle
  shells
• Marine mollusks substitute strontium for Ca
• Biological interactions (grazing, competition,
  predation)
• Influences stream organism communities
• Ex lots of grazers ? reduced periphyton size and
  tightly clinging diatoms
• few grazers ? long filamentous green algae

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• Disturbance
• Stream channel morphology is unstable, modified
  during high discharge events
• Poor forest practices can cause heavy
  sedimentation
• Ex filamentous algae in the Eel River
• - High discharge during the previous winter and
  spring kill many caddis flies that feed on the
  filamentous algae (i.e. less grazers)
• Thus, in drought years, more caddis flies ? algae
  is controlled

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Categories of Organic Matter in Streams

• CPOM greater than 1 mm in size
• includes leaves, needles, bark, twigs, other
  plant parts
• FPOM less than 1 mm, greater than 0.5 ?m
• DOM less than 0.5 ?m
• Aquatic organisms utilize little DOM directly,
  usually POM is the major food source
• Periphyton attached algae
• Macrophytes higher aquatic plants

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Organic Matter Dynamics

• Reduced organic matter energy source of stream
  ecosystems
• Breakdown of allochtonous materials from CPOM to
  FPOM
• Biological breakdown as well as mechanical
  fragmentation due to current velocity and
  transport

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• Three stages in allochtonous material breakdown
• leaching of soluble constituents such as proteins
  and some carbohydrates
• colonization and decomposition by aquatic
  hyphomycetes (fungi) and bacteria
• feeding by macroinvertebrates
• Much of the nutrition is from the attached
  microbial flora

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River Continuum Concept

• Discusses changes as stream order increases in
  the
• light regime
• temperature regime
• importance of allochtonous inputs
• importance of autochthonous inputs
• CPOM/FPOM ratio
• photosynthesis/respiration ratio
• stream organisms

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Good References

• Eynes, Ecology of Running Waters
• Reid, Ecology of Inland Waters and Estuaries
• Mount, California Rivers and Streams